So I am putting together a AR and want to do a flat top. What is the difference between a A3 and A4 flat top?
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So I am putting together a AR and want to do a flat top. What is the difference between a A3 and A4 flat top?
I don't believe this to be necessarily true. The A3 has been used for a long time by Colt to designate flat-top AR-15s (AR-15A3), even before the adoption of flat-top rifles as standard by the military. You need to distinguish between military designations and civilian ones.
Now a lower question. I have a lower stamped multi cal.
I see companies that make one lower but have different caliber uppers, ie, .556, .22, 6.8, 5.45x39, etc. Can a "standard" multi cal lower be used on the complete uppers of these different calibers?